Description of the Related Art
The invention relates to a lighting device for an oven, in particular a household oven, the closed baking chamber of which can be acted upon by microwave energy, including an incandescent bulb mounted on a bulb holder and supplied with current from outside the baking chamber through electrical connection lines.
In microwave ovens or microwave stoves with or without additional thermal heat sources, lighting devices having incandescent filament bulbs are used for lighting the baking chamber. In such devices, the bulbs are typically disposed on the wall of the baking chamber in the vicinity of one of the side walls or the upper wall of the baking chamber. As is well known in this connection, a relatively large opening must be provided in the baking chamber wall, behind which the lamp base of the lighting device is secured outside the oven space. Special means must be made in this vicinity in order to prevent the escape of microwaves through the openings. Furthermore, the fact that the incandescent bulbs with the incandescent filaments and incandescent filament holders thereof act as receiving antennae for microwave energy radiated into the baking space must also be taken into account. Among other effects, the voltages induced in such lighting systems generate currents which cause current to flow over the incandescent filaments. The incandescent coils of prior art lighting devices can and are made to become incandescent, solely due to the action of these currents. If these currents are superimposed on the currents supplied for purposes of continuous illumination, then the typical incandescent bulbs which are used would be rapidly destroyed by the overload The electromagnetic microwave field moves around within the baking space, among other reasons for the sake of attaining the most uniform possible exposure to microwaves in the baking chamber. However, at least in the prior art lighting devices that are exposed to microwave energy, this causes the incandescent bulb to light up intermittently, which is annoying. For these reasons, it is the usual practice to provide ways of preventing or at least of reducing microwave energy from being radiated onto the incandescent bulb of the lighting device. The most often used means of protection shade the lighting device from the space acted upon by microwave energy with a so-called perforated screen formed of metal material. Since the incandescent bulbs should be accessible and capable of being changed from inside the baking space, especially in built-in appliances, the perforated screen must be detachably secured on the baking space wall, which once again presents problems in terms of microwave shielding. Furthermore, a particular disadvantage is the fact that the perforated screen sharply reduces the luminous efficiency. In order to adequately light the baking space, correspondingly powerful bulbs must be used, which in turn present additional problems because of their pronounced heat buildup.
It has also already been proposed to shift the incandescent bulbs back behind the baking space wall, and to form the socket shaft for the incandescent bulb in the form of so-called microwave traps. This structure once again meets with considerable difficulties in practical utilization and the incandescent coil that is shifted out of the baking space again leads to reduced luminous efficiency.
It is accordingly an object of the invention to provide a lighting device for an oven capable of being acted upon by microwave energy, in particular a household oven, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which assures good illumination of a baking space that is capable of being acted upon by microwave energy without the above-described unfavorable secondary effects resulting from the action of microwave properties.